Djurleite is a

copper sulfide Copper sulfides describe a family of chemical compounds and minerals with the formula CuxSy. Both minerals and synthetic materials comprise these compounds. Some copper sulfides are economically important ores. Prominent copper sulfide mineral ...

mineral of secondary origin with formula Cu₃₁S₁₆ that crystallizes with

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic s ...

-prismatic symmetry. It is typically massive in form, but does at times develop thin tabular to prismatic crystals. It occurs with other supergene minerals such as

chalcocite Chalcocite (), copper(I) sulfide (Cu2S), is an important copper ore mineral. It is opaque and dark gray to black, with a metallic luster. It has a hardness of 2.5–3 on the Mohs scale. It is a sulfide with a monoclinic crystal system. The ...

covellite Covellite (also known as covelline) is a rare copper sulfide mineral with the formula CuS. This indigo blue mineral is commonly a secondary mineral in limited abundance and although it is not an important ore of copper itself, it is well known t ...

and

digenite Digenite is a copper sulfide mineral with formula: Cu9S5. Digenite is a black to dark blue opaque mineral that crystallizes with a trigonal - hexagonal scalenohedral structure. In habit it is usually massive, but does often show pseudo-cubic f ...

in the enriched zone of copper

ore Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 Apr ...

bodies. It is a member of the chalcocite group, and very similar to chalcocite, Cu₂S, in its composition and properties, but the two minerals can be distinguished from each other by

x-ray powder diffraction An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30 ...

. Intergrowths and transformations between djurleite, digenite and chalcocite are common.Pósfai, M. & Buseck, P. R. (1994): Djurleite, digenite, and chalcocite: Intergrowths and transformations. American Mineralogist, 79, 308-315 Many of the reported associations of digenite and djurleite, however, identified by powder diffraction, could be anilite and djurleite, as anilite transforms to digenite during grinding. Djurleite was named for the Swedish chemist Seved Djurle (1928–2000), from the

University of Uppsala Uppsala University ( sv, Uppsala universitet) is a public research university in Uppsala, Sweden. Founded in 1477, it is the oldest university in Sweden and the Nordic countries still in operation. The university rose to significance during ...

, Sweden, who first synthesized the mineral in 1958, prior to its discovery in nature. The natural material was first described in 1962 by E H Roseboom Jr, of the

US Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, an ...

, from occurrences at the type locality,

Barranca del Cobre Copper Canyon (Spanish: Barrancas del Cobre) is a group of six distinct canyons in the Sierra Madre Occidental in the southwestern part of the state of Chihuahua in northwestern Mexico that is in size. The canyons were formed by six rivers th ...

, Chihuahua, Mexico.Roseboom, E.H. (1962) Djurleite, Cu_1.96S, a new mineral. American Mineralogist: 47: 1181-1184.

The chalcocite group

The chalcocite group is a group of closely related copper sulfides, with the formulae: *

Chalcocite Chalcocite (), copper(I) sulfide (Cu2S), is an important copper ore mineral. It is opaque and dark gray to black, with a metallic luster. It has a hardness of 2.5–3 on the Mohs scale. It is a sulfide with a monoclinic crystal system. The ...

(two polymorphs) Cu₂S * Djurleite Cu₃₁S₁₆ (Cu_1.94S) *

Digenite Digenite is a copper sulfide mineral with formula: Cu9S5. Digenite is a black to dark blue opaque mineral that crystallizes with a trigonal - hexagonal scalenohedral structure. In habit it is usually massive, but does often show pseudo-cubic f ...

(Cu_1.80S) * Roxbyite (Cu_1.78S) *

Anilite Anilite ( IMA symbol: Ani) is a mineral with the chemical formula CuS. It is named for its type locality, the Ani Mine in Akita Prefecture.Anilit ...

Cu₇S₄ (Cu_1.75S) *

Geerite Geerite is a copper sulfide mineral with the chemical formula Cu8S5. The mineral is named after the original collector, Adam Geer, of Utica, New York, US. Crystallography Geerite is in the crystal class . This means that the crystal could be inv ...

Cu₈S₅ (Cu_1.60S) * Spionkopite (Cu_1.32S) *

Covellite Covellite (also known as covelline) is a rare copper sulfide mineral with the formula CuS. This indigo blue mineral is commonly a secondary mineral in limited abundance and although it is not an important ore of copper itself, it is well known t ...

(CuS)

Unit cell

Djurleite has a

structure with a large

unit cell In geometry, biology, mineralogy and solid state physics, a unit cell is a repeating unit formed by the vectors spanning the points of a lattice. Despite its suggestive name, the unit cell (unlike a unit vector, for example) does not necessaril ...

containing 248

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

and 128

sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...

atoms.H. T. Evans "Djurleite (Cu1.94S) and Low Chalcocite (Cu₂S): New Crystal Structure Studies
Science 203 (1979) 356
/ref> The formula is Cu₃₁S₁₆,

molar mass In chemistry, the molar mass of a chemical compound is defined as the mass of a sample of that compound divided by the amount of substance which is the number of moles in that sample, measured in moles. The molar mass is a bulk, not molecular, p ...

2483 g, and there are 8 formula units per unit cell (Z = 8). The crystal class is 2/m, meaning the structure has an axis of twofold rotational symmetry perpendicular to a

mirror plane In mathematics, a reflection (also spelled reflexion) is a mapping from a Euclidean space to itself that is an isometry with a hyperplane as a set of fixed points; this set is called the axis (in dimension 2) or plane (in dimension 3) of refle ...

. The

space group In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it unchan ...

is P2₁/c, and the unit cell parameters are a = 26.897 Å, b = 15.745 Å, c = 13.565 Å and β = 90.13°. The structure is based on hexagonal closest packing of sulfur atoms with a monoclinic space group.Klein et al (1993) Manual of Mineralogy 21st Edition, Wiley

Physical properties

Crystals are short prismatic and thick tabular, but the mineral usually occurs in a massive and compact form. There is no cleavage. Pseudohexagonal

twins Twins are two offspring produced by the same pregnancy.MedicineNet > Definition of TwinLast Editorial Review: 19 June 2000 Twins can be either ''monozygotic'' ('identical'), meaning that they develop from one zygote, which splits and forms two em ...

are common, with crystal blocks rotated around the a

crystal axis In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric patterns t ...

, which is normal to the

close-packed In geometry, close-packing of equal spheres is a dense arrangement of congruent spheres in an infinite, regular arrangement (or lattice). Carl Friedrich Gauss proved that the highest average density – that is, the greatest fraction of space occu ...

layers, by multiples of 60°. Djurleite is brittle, with a conchoidal (shell-like)

fracture Fracture is the separation of an object or material into two or more pieces under the action of stress. The fracture of a solid usually occurs due to the development of certain displacement discontinuity surfaces within the solid. If a displa ...

. It is a soft mineral, with

hardness In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard ...

to 3, a little less than that of

calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

. The

specific gravity Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water (molecule), wa ...

, 5.63, is high, due to the copper content, djurleite is denser than the copper-iron sulfide

bornite Bornite, also known as peacock ore, is a sulfide mineral with chemical composition Cu5 Fe S4 that crystallizes in the orthorhombic system (pseudo-cubic). Appearance Bornite has a brown to copper-red color on fresh surfaces that tarnishes to v ...

, but not as dense as the iron-arsenic sulfide

arsenopyrite Arsenopyrite ( IMA symbol: Apy) is an iron arsenic sulfide (FeAsS). It is a hard ( Mohs 5.5-6) metallic, opaque, steel grey to silver white mineral with a relatively high specific gravity of 6.1. When dissolved in nitric acid, it releases eleme ...

Optical properties

Djurleite is grey, blue-black or black, with a black streak and a submetallic to metallic luster. It is an opaque mineral, so

refractive indices In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. The refractive index determines how much the path of light is bent, or ...

are not defined. The reflectivity (the percentage of incident energy which is reflected from a surface) for light of

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...

540 nm varies between 29.6 and 30.2, and is slightly dependent on the direction of the incident light, that is to say, the mineral is weakly

anisotropic Anisotropy () is the property of a material which allows it to change or assume different properties in different directions, as opposed to isotropy. It can be defined as a difference, when measured along different axes, in a material's physic ...

Environment

Djurleite is a widely distributed but little known ore mineral of copper, found in the secondary enrichment zones of

deposits, associated with other secondary copper sulfides

chalcopyrite Chalcopyrite ( ) is a copper iron sulfide mineral and the most abundant copper ore mineral. It has the chemical formula CuFeS2 and crystallizes in the tetragonal system. It has a brassy to golden yellow color and a hardness of 3.5 to 4 on the Mo ...

and

anilite Anilite ( IMA symbol: Ani) is a mineral with the chemical formula CuS. It is named for its type locality, the Ani Mine in Akita Prefecture.Anilit ...

with

pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic Luster (mineralogy), lust ...

Occurrence

The type locality is

Barranca de Cobre Copper Canyon (Spanish: Barrancas del Cobre) is a group of six distinct canyons in the Sierra Madre Occidental in the southwestern part of the Mexican state, state of Chihuahua (state), Chihuahua in northwestern Mexico that is in size. The can ...

, Chihuahua, Mexico, and the type material is conserved at the

Royal Ontario Museum The Royal Ontario Museum (ROM) is a museum of art, world culture and natural history in Toronto, Ontario, Canada. It is one of the largest museums in North America and the largest in Canada. It attracts more than one million visitors every year ...

, Toronto, Canada, M25369, and at the

National Museum of Natural History The National Museum of Natural History is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. It has free admission and is open 364 days a year. In 2021, with 7 ...

, Washington, DC, US.

References

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External links

* JMol: http://rruff.geo.arizona.edu/AMS/viewJmol.php?id=10818 Sulfide minerals Copper(I,II) minerals Monoclinic minerals Minerals in space group 14